It is priorly known to provide a conduction path between two contact locations of which one is movable on a circular path, while the other is disposed stationary outside such circular path. Apparatus having such conductor paths include, for instance, cable coilers in which the electric cable or cord is wound on a reel. The cord can be pulled out of the housing of the apparatus. Under the action of a spring it is automatically rolled up again after a pulling force is removed. One essential problem here is the transfer of current from the stationary firm attachment of the apparatus to the end of the line which is arranged turnably on the spool.
For the transfer of current between contact locations which move relative to each other, wiper contacts or rings are priorly known. Such arrangements are subject to wear and are at a disadvantage in the case of low current intensities because of higher transfer resistances.
U. S. Pat. No. 4,696,523, issued Sept. 29, 1987, is directed to a priorly known apparatus including a conductive path between two contact locations which are rotatable with respect to each other. In this apparatus, the conduction path is comprised of a flat ribbon cable wound in the manner of a coiled spring. Upon the rotation of on of the contact locations in one direction, the windings of such coiled spring are pulled together to reduce the diameter of the coiled spring, while rotation in the opposite direction causes the windings of such coil springs to expand and increase the diameter of the coiled spring. Accordingly, the relative movement of the two contact locations connected by such coiled spring results in a "breathing motion", similar to a watch spring. To protect against the considerable mechanical stress and kinking of the end portions of the flat ribbon cable firmly attached to the corresponding contact locations, such prior art apparatus include strip-shaped stabilizers at each of the connections between the flat ribbon cable and the contact locations each of such stabilizers being of dimensionally stable plastic and having a U-shaped cross section for closely enclosing the associated end portion of the flat ribbon cable.
U. S. Pat. No. 4,836,795, issued June 6, 1989, is directed to a priorly known apparatus for providing an electrical conduction path between a first contact location rotatable a plurality of rotations, in either direction, about a longitudinal axis, and a stationary contact location positioned radially from the rotatable contact location. Such apparatus is comprised of a bifilar spiral spring formed of a length of flat ribbon cable having at least two electrical conductors. The bifilar spiral coil spring is secured only by firmly attached connections at its opposite ends to the two contact locations; whereby it uncoils and slidably moves in response to the direction of rotation of the rotatable contact location, and upon reversal of such rotation, recovers its original shape and position between the two contact locations.
U. S. Pat. No. 4,927,365, issued May 22, 1990, is directed to a priorly known apparatus comprising an electrical conductive path between two contact locations rotatable, one with respect to the other. The electrical conduction path comprises a flat ribbon cable, including at least two electrical conductors, that is wound in the manner of a coiled spring. The flat ribbon cable is firmly attached at a first end thereof to one of the contact locations, while the other end thereof is firmly attached to the other contact location. To protect the flat ribbon cable from kinking and mechanical damage at each of the ends thereof, each end portion thereof is folded across an immediately adjacent portion and a stabilizer connection assembly is positioned to extend across both such portions. Each such assembly is comprised of a protective sheath of flexible insulating material positioned closely about the folded end portion, and an angular attachment of molded insulating material, including a clamping segment and a ribbon-shaped segment extending at an angle one to the other.
With all such prior art apparatus wherein a flat ribbon cable is provided between a first contact location rotatable a plurality of rotations in either direction, about a longitudinal axis, and a stationary contact location positioned radially from the rotatable contact location, the connected ends of the flat ribbon cable are subject to damage due to tension and bending stresses. Additionally, since such cables often comprise a plurality of electrical conductors of minimal, flat cross-sections, their ability to withstand such high tension and bending stresses is quite limited.